As an example of melt-solidified substance, a welded pipe made of phosphorus-deoxidized copper is well known as a welded substance. It has a problem of weak strength caused by the coarsening of grains in the welded areas. As a result, it has been proposed that a copper alloy produced by adding Fe or Co to phosphorus deoxidized copper is used to make a welded pipe in order to prevent the grains in the welded areas from coarsening as much as possible. For example, Patent Document 1 discloses a seamless copper alloy pipe for heat exchanger composed of 0.005 to 0.8 mass % of Fe, 0.01 to 0.026 mass % of P, 0.005 to 0.3 mass % of Zr, 3 to 30 ppm of O2 and the remainder Cu, and Patent Document 2 discloses a seam welded copper alloy pipe for heat exchanger having a composition, in which 0.02 to 0.2% of Co, 0.01 to 0.05% of P, 1 to 20 ppm of C (if necessary), the remainder Cu and inevitable impurities are contained, and the content of oxygen, as an inevitable impurity, is restricted to 50 ppm or less.
Patent Document 1: JP-B-58-039900
Patent Document 2: JP-A-2000-199023